Netstar refusing to cancel policy

I have had the worst experience with netstar. These guys are recommended to me by Outsurance. I sold my vehicle on Monday and I called them to cancel. To date this not cancelled. I spoke to this call centre guy Mario who was rude and antagonistic as soon as I said I wanted to cancel. He further was forcing me to agree with paying almost R600 to cancel my account. I told him that I do not agree to this pressure of being forced to pay R600 when the vehicle is not mine. Further I told him that he needs to send me communication as this in violation the CPA and I need legal to check. He did not like my answer even though I asked to speak to his manager. He cut me off. Mario is a bully and does not know how to deal with customer. He should be disciplined for cutting me off.